The aorta is the major artery that carries blood from the heart to the rest of the body.
Aortic dissection occurs when the inner layer of the aortic wall (intima) tears, leading to blood flow through the tear, causing separation of the middle and inner layers of the artery wall (dissection). When blood flow dissects the artery wall, it forms a second channel for flow, creating what is termed a “false lumen”. The original flow lumen in the aorta is termed “true lumen”. These two channels compete for blood flow, sometimes leading to poor or absent flow in the true lumen and can impede perfusion of vital structures downstream such as the renal and visceral arteries. When perfusion of important arteries is impaired, this is termed “complicated” dissection. This can occur in any artery, but most often develops in areas of high pressure and shear stress like the ascending aorta (the first segment of the aorta), where the aorta originates from the heart's left ventricle (pumping chamber). This is the part of the aorta closest to the heart (thus the name “proximal aorta”). Aortic dissection can also occur in other parts of the aorta.
The main risk factors for development of aortic dissection are atherosclerosis (hardening of the arteries) and high blood pressure. According to American Heart Association WEBSITE, high blood pressure is the most common factor predisposing the aorta to dissection. Preventive measures to reduce and control blood pressure and reduce atherosclerosis can reduce the risk of developing aortic dissection. In addition, traumatic injury is a major cause of aortic dissection, especially blunt trauma to the chest, or deceleration injury leading to aortic lining tears. Other risk factors and conditions associated with the development of aortic dissection include bicuspid aortic valve, coarctation (narrowing) of the aorta, connective tissue disorders, Ehlers-Danlos syndrome, heart surgery or procedures, Marfan syndrome, pregnancy, pseudoxanthoma elasticum, aortic dilation, aortic aneurysm, and congenital aortic valve abnormalities.
Acute aortic dissection can cause sudden chest, back, or abdominal pain. This pain is often described as a tearing sensation, and can be very painful. The pain may be localized to the front or back of the chest. Other symptoms and signs depend on the arterial branches involved and compression of nearby organs. Men are more prone to develop aortic dissection (male-to-female ratio ranges from 2:1 to 5:1). Aortic dissection occurs in roughly 2 out of every 10,000 people, although some estimates are significantly higher.
Upon reporting symptoms, the health care provider quickly obtains a patient's history and performs a thorough physical exam. A “blowing” murmur over the aorta, a heart murmur, or other abnormal sound may be heard. For some patients, there may be a difference in blood pressure between the right and left arms, or between the arms and the legs. Some patients may exhibit low blood pressure, bulging neck veins, or signs resembling a heart attack. The patient may exhibit signs of shock, but with normal blood pressure. They may also have abdominal pain related to mal-perfusion of organs. Aortic dissection or aortic aneurysm may be seen with commonly used imaging techniques including aortic angiography, chest x-ray which may show chest widening or fluid in the lining of the lung (pleural effusion), chest MRI, CT scan of chest with dye, Doppler ultrasonography, echocardiogram, and transesophageal echocardiogram (TEE).
Acute aortic dissection is an emergency condition, and medical treatment should start as soon as possible. The patient often is admitted to an intensive care unit, and drugs to lower blood pressure and heart rate are given. In some cases emergency surgery is needed. Alternative procedures, such as placing a stent inside the aorta, are being used more frequently. The goal of treatment is to prevent complications. Hospitalization generally is required. Surgery to repair or replace the damaged section of aorta can treat the condition in some cases. If the aortic valve is damaged, valve replacement may be necessary. If the heart arteries are involved, a coronary bypass may also be performed. Aortic dissection is a life threatening disease. The condition can be cured with surgery if it is done before the aorta ruptures or organs fail from low blood flow. Most patients who have rupture after aortic dissection do not survive. Complications from aortic dissection can include aortic aneurysm formation with or without rupture, aortic valve compromise, stroke, paralysis, kidney failure, limb loss, bowel compromise and death.